Systematics Section / ASPT
Whitlock, Barbara A. , Wilkins, Carol F. .
Multiple independent dispersal events out of Australia in Lasiopetaleae (Malvaceae s.l.).
LASIOPETALEAE are a well-supported clade including 10 genera and ca. 200 species of primarily shrubs with small capsular fruit and ant-dispersed seeds. The vast majority of species occurs in Australia, inhabiting all states and territories. However, at least five species occur outside of Australia: in New Guinea, New Caledonia, Madagascar and southeast Asia. The biogeographic history of these disjunct taxa has been unclear partly due to problems with taxonomy and generic limits; nevertheless, these distributions have been the subject of past speculation. For example, Rulingia and Keraudrenia have been cited as examples of genera with rare disjunctions between Australia and Madagascar, presumably the result of long distance dispersal. Here, we investigate the relationships and divergence times of species of Lasiopetaleae occurring outside Australia using phylogenetic and molecular clock analyses. Morphological evidence and DNA sequence data indicate that the distributions of all five species represent independent dispersal events. Molecular clock analyses of chloroplast data suggest that two of these species, Rulingia madagascariensis and Maxwellia lepidota, occurring in Madagascar and New Caledonia respectively, last shared common ancestors with Australian lineages before the aridification of Australia in the Tertiary. Keraudrenia macrantha, the second Malagasy taxon, is currently known from one type specimen. While no sequence data exist for this under-collected species, we hypothesize based on its morphology that it may also have diverged early within the history of the Lasiopetaleae. In contrast, Commersonia bartramia, occurring in New Guinea and widely in Australasia, has more recent connections to Australia and is closely related to Lasiopetaleae from Queensland. Finally, we use Lasiopetaleae to test the common assumption that the area of highest diversity equals the area of origin. These data illustrate the advantages of a phylogenetic approach in revealing complex biogeographic patterns.
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1 - University of Miami, Department of Biology, 1301 Memorial Drive, Coral Gables, Florida, 33124, USA
2 - University of Western Australia, School of Plant Biology (Botany M090), 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
Presentation Type: Oral Paper:Papers for Sections
Location: 134/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 12:15 PM